RFR(S): Fix regression test for 8012015 (Use PROT_NONE when reserving memory)

[Mikael Vidstedt]

Please review the below change:

Webrev: http://cr.openjdk.java.net/~mikael/webrevs/8013726/webrev.03/webrev/
Bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8013726


Background (see bug report for some additional information):

When changing the protection for reserved memory [1][2] I also added a 
regression test. The test is supposed to reserve a memory range and 
explicitly provoke a crash by accessing that memory. Unfortunately the 
test is severely broken and does not work on all platforms. Specifically 
it has the following problems:

* It tries to reserve a 4kb memory range, which is not always allowed - 
os::vm_allocation_granularity() is the memory allocation granularity. 
For example, on my windows machine the granularity is 64kb. This 
triggers the assert in the bug report.

* The test also uses Unsafe to do the memory access, but signals raised 
by Unsafe operations are handled slightly differently from normal memory 
accesses. Specifically, a SIGBUS signal is translated into a Java 
exception. Furthermore, on OSX a memory access in reserved memory raises 
a SIGBUS whereas on other platforms (Linux, Solaris) it is a SIGSEGV.


About the change:

The change resolves the assert by using os::vm_allocation_granularity() 
when specifying the size of the reserved memory.

In order to avoid the Unsafe specific behavior in combination with the 
platform specific signal raised the memory access has also been moved 
into the native whitebox code. The function now both does the memory 
reservation and touches the memory and it has been renamed to reflect 
that. One alternative to that would be to have a separate whitebox 
function to read from a memory address, but that did not immediately 
make sense. Future tests may want to revisit that.

Thanks,
Mikael

[1] http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8012015
[2] http://hg.openjdk.java.net/hsx/hotspot-rt/hotspot/rev/f32b6c267d2e